Single-ended jacketed arc lamp mounting



May 3, 1966 L. J. SMIALEK ETAL SINGLE-ENDED JACKETED ARC LAMP MOUNTINGFiled April 30, 1962 ITWVTWTOTSI Leon d. Smiatek Ctaven 6 .Cook by JTheir" A t tow-neg United States. Patent 3,249,781 SINGLE-ENDED JAQKETEDARC LAMP MOUNTING Leon J. Smialek, Chagrin Falls, and Clarence G. Cook,East Cleveland, Ohio, assignors to General Electric Company, acorporation of New York Filed Apr. 30, 1962, Ser. No. 191,207 7 Claims.(Cl. 31325) The invention relates to an elongated single-ended jacketedarc lamp having a base at one end only for engagement in a socket. Theinvention is more particularly concerned with the mount within thejacketed assembly for supporting the arc tube within the jacket and formaking electrical connections to its electrodes.

The light source proper of the present lamp is a high pressure mercuryvapor arc lamp in the form of anelongated quartz tube having a lengthmany times greater than its diameter with electrode inleads sealed intoopposite ends. These lamps are efiicient sources of ultravioletradiation and are used extensively in photochemical applications. Theymay also be used for general illumination when suitable glass shieldsare provided for cutting out the ultraviolet radiation which is harmfulto the eyes.

In order to. prevent oxidation of the inleads of the quartz arc tube, itis mounted within an outer glass jacket which is then evacuated orfilled with a neutral gas. With tubes of great length, and by such ismeant an arc tube having a length 20 or more times greater than itsdiameter, a double-ended jacket has generally been used. This is ajacket provided with terminals at both ends and wherein the arc' tube issupported at both ends. For certain applications however, such as inphotochemical treatment of fluids where the lamp is suspended and hangsdown in a fluid bath, a single-ended jacket is necessary.

The problems involved in mounting an arc tube of great length in asingle-ended jacket and in making electrical connections from the jacketbase to the arc tube terminals are considerable, and the object of theinvention is to provide a convenient and practical means for so doing.

More specific objects and corresponding features desired in the mountingarrangement according to the invention are ruggedness with sufiicientflexibility to absorb shock or vibration, ease of assembly andadjustability for normal variations in arc tube and jacket length.

In accordance with our invention, the arc tube is supported within thejacket between a pair of apertured end plates which engage and arecaused to press against the shoulders of the arc tube about the seals ofthe inleads by means of a pair of side rods running the full length ofthe arc tube or chamber and maintained 'under spring tension. One ofthese rods is used as the current carrying conductor to the arc tubeinlead at the far end of the jacket and the two together result in abalanced structure which remains aligned under tension. During operationof the lamp, the heat therefrom causes the rods to expand and lengthenbut the springs which keep them under tension take up the increase inlength so that the arc tube remains firmly and securely mounted at alltimes.

Other objects of the invention and further features and advantagesthereof will be apparent from the description hereinafter following andfrom the accompanying draw ing illustrating a preferred embodiment. Thefeatures of the invention believed to be novel will be more particularlypointed out in the appended claims.

' In the drawing:

FIG. 1 is a full side view of a high pressure singleended mercury vaporarc lamp of great length embodying the invention.

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FIG. 2 is a side view, partly sectioned but foreshortened and to alarger scale, of the same lamp.

FIG. 3 is an exploded pictorial view showing fragments of the same lamp.at the levels of the arc tube shoulders and at an intermediate point.

Referring to the drawing and more particularly to FIGS. 1 and 2, theillustrated lamp 1 comprises an inner arc tube 2 coaxially mountedwithin an outer envelope or jacket 3. The arc tube is a cylindricalquartz tube filled with an inert gas-such as argon at a low pressure,for instance 25 millimeters of mercury, and a quantity of mercurysufficient when vaporized to develop a vapor pressure in the range of 1to 10 atmospheres, for instance 2 to 4 atmospheres, the mercury beingindicated by the droplet 4. At each end of the lamp there is provided athermionic electrode5 mounted on a support rod 6 and to which currentconnections are made through an inlead which extends through a generallycylindrical axially projecting quartz seal body 7. Each inlead comprisesa thin metal foil portion 8, commonly made of molybdenum, with a shortrod-like portion 9 emerging from the end of the seal body. The centralportion of the inlead is Very thin, for instance less than 1 mil inthickness, so that it yields under tension to the quartz during coolingand does not rupture nor crack the quartz, thereby preserving a hermeticseal. The illustrated seal is generally known as a vacuum seal becausevacuum is used to collapse the originally hollow quartz seal body 7 ontothe inlead 8 passing therethrough while the quartz is heated tosoftening temperature. Other seal constructions may of course be used.

The outer envelope or jacket 3 consists of a hard glass such as aborosilicate glass and is generally tubular with a rounded orhemispherical closure 11 at its lower or far end. The upper or near endof the jacket is necked down at 12 and is closed by a cup-shaped closuremember 13 which is termed a bipost flare. The bipost flare is made as aseparate assembly and comprises a shallow cup-like member 14 of hardborosilicate glass provided with a central exhaust tube 15 (shown tippedoff) and a pair of outwardly projecting teat-like extensions 16. A pairof hollow copper pins or posts 17 are sealed peripherally into theextensions 16, whence the name bipost flare. The posts 17 are closed atthe outer end and are enlarged at the inner end with a feathered edge 18which is sealed to the flare by embedding it in the lip of theprojecting teat 16. Due to the thinness of the metal at the edges of thepost body where it is sealed to the glass, a hermetic joint is achievedwhich can withstand substantial temperature variations. Theinter-envelope space between the arc tube and outer jacket is eitherevacuated or, preferably, is filled with a nonoxidizing gas such asnitrogen at a pressure, for instance, of 200 millimeters of mercury.

Mechanical support for and electrical connections to the arc tube fromthe posts 17 are provided by a pair of support rods 20, channel-shapedin cross section. The rods are suitably fastened within the hollow postsand extend inwardly into the jacket. The arc tube is located between apair of end plates 21, 22, each plate having a central aperturetherethrough which bears against the shoulder 23 of the arc tube aboutthe seal body 7. The plates are drawn together by means of long tie rodswhich extend the length. of the arc tube, the tie rods being fastenedinto the ends of the support rods 20 in suitable fashion, as by weldingor by crimping the latter. One tie rod 24 (on the left side) iscontinuous and provides a circuit connection from one of the posts 17 tothe electrode at the far end of the arc tube by means of a flexiblejumper or strap 25. The other tie rod is in two parts: 26a, 26b whichare mechanically joined together by a Patented May 3, 1966 V 3 ceramicinsulator 27 but electrically insulated thereby one from the other. Part26a which is fastened to one of the support rods 20 provides circuitcontinuity from the other post 17 to the electrode at the near end ofthe arc tube by means of a flexible strap or jumper 2%.

It is desirable to insulate the end plates electrically and thermallyfrom the tie rods in order to avoid electrical stress and excessivecooling about the shoulders of the arc tube. To this end, end plate 21is clampedbetween the mating parts 2%, 2% of ceramic insulators whichare locked in place by nuts 30 engaging the threaded ends of the tierods. These insulators are of the kind commonly known as feed-throughinsulators, and part 2% is provided with a neck which extends through anoversize hole in plate 21, thereby serving to insulate the plate fromthe rod in the usual fashion. The remote end plate 22 is engaged bysimilar feed-through insulator parts 3112 which make a sliding fit onthe tie rods. The other insulator parts 31a are retained at the outerends of the tie rods by means of locking nuts 32, and coil springs 33located between the insulator parts cause end plate 22 to pressresiliently against the end of the arc tube.

End plate 22 is provided with a loop or harp 34 consisting of aresilient U-shaped metal band which presses resiliently against therounded end of the jacket and serves to relieve some of the strain onthe posts 17 resulting from axial .shocks to the lamp in use or inhandling. A springy transverse metal blade 35 is welded across the endof the harp and serves to maintain it centered in the end of the jacket.Both end plates 21, 22 are furthermore provided with springy lateralmetal blades 36 which are curved not quite to the radius of the jacketin order that their ends press resiliently against the jacket tomaintain the plates axially centered. The tie rods 24, 26b are providedwith alignment rings 37 which are Welded to the tie rods at spacedpoints along their length. The rings have curved springy metal blades 38welded to them on opposite sides and the ends of these blades bearagainst the jacket to maintain the assembly properly centered within thejacket. Although the alignment rings 37 provide electricalinterconnection of the tie rods 24 and 2612, this does not create anyproblem because the short tie rod section 26a is insulated from theremainder.

The mounting arrangement which has been described achieves strength sothat it does not distort under the weight of the arc tube and at thesame time has sufiicient resiliency that the shocks encountered inshipping and handling or during operation will not damage the assembly.By reason of the coiled springs 33, the tie rods are maintained intension and this is highly desirable to prevent distortion and twistingof the rods and mount assembly as the rods heat up during operation ofthe lamp. The are tube is maintained in compression wherein glass orquartz is strong. In tests performed without the springs 33 and whereinthe end plates 21, 22 were both rigidly attached to the tie rods, thetie rods expanded to the point where the arc tube was quite loosebetween the end plates and as a result of distortion and twisting of theside rods, they touched either the jacket or the arc tube wall in one ormore places. With the coiled springs, the expansion of the rods is takenup by the springs and the rods remain perfectly straight and the entireassembly maintains its alignment.

As an example of a high power photochemical lamp actually constructed inaccordance with the illustration of the drawings and successfullytested, the following data apply:

Electrical.l0,000 watts, 1400 volts 8.15 amperes (87.5% power factor).

Burning position.Vertical only immersed in fluid at 75 C. maximumtemperature.

Jacket dimensi0ns.-71 A" overall length x 3" diameter.

Arc tube dimensi0ns.-59 /2" interelectrode distance x inch oute dameter- The preferred embodiment of the inventionwhich has beendescribed herein is intended by way of example and not in order to limitthe invention thereto. The scope of the invention is to be determined bythe appended claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A single-ended jacketed arc lamp of great length comprising an innerarc tube, a tubular light-transmitting jacket surrounding said arc tubeclosed at the far end, and a mounting structure supporting said are tubewithin said jacket comprising terminals sealed through the near end ofsaid arc tube, a pair of tie rods extending on opposite sides of saidare tube and fastened to said terminals, 9. pair of transverse endplates supported by said tie rods near opposite ends thereof, each plateengaging an end of the arc tube, one of said end plates being slidablymounted on said tie rods, and spring means urging the slidably mountedend plate against the arc tube so as to maintain the tie rods in tensionand the arc tube in compression in spite of expansion of the tie rodsfrom heat during operation of the lamp.

2. A single-ended jacketed arc lamp of great length comprising an innerarc tube, a tubular light-transmitting jacket surrounding said arc tubeclosed at the far end, and a mounting structure supporting said are tubewithin said jacket comprising terminals sealed through the near end ofsaid are tube, a pair of tie rods extending on opposite sides of saidare tube and fastened to said terminals, a pair of transverse end platessupported by said tie rods near opposite ends thereof, each plateengaging an end of the arc tube, the near end plate being fast to saidtie rods, the far end plate being slidably mounted on said tie rods, andcoil springs fastened to said tie rods and urging the slidably mountedend plate against the arc tube so as to maintain the tie rods in tensionand the arc tube in compression in spite of expansion of the tie rodsfrom heat during operation of the lamp.

3. A single-ended jacketed arc lamp of great length comprising an innerarc tube having electrode inleads at opposite ends, a tubularlight-transmitting jacket surrounding said are tu-be closed at the farend, and a mounting structure supporting said are tube within saidjacket comprising terminals sealed through the near end of said aretube, a pair of tie rods extending on opposite sides of said arc tubesubstantially its full length and fastened to said terminals, a pair ofend plates supported by said tie rods near opposite ends thereof, eachplate engaging an end of the arc tube, one of said end plates beingslidably mounted on said tie rods, spring means urging the slidablymounted end plate against the are tube so as to maintain the tie rods intension and the arc tube in compression in spite of expansion of the tierods from heat during operation of the lamp, a connection from theelectrode inlead at the far end of the arc tube to one of said tie rods,an insulator interposed in the other of said tie rods, and a connectionfrom the electrode inlead at the near end of said are tube to theportion of said other tie rod between the jacket terminal and saidinsulator.

4. A single-ended jacketed are lamp of great length comprising an innerarc tube having projecting seal bodies at opposite ends, a tubularlight-transmitting jacket surrounding said arc tube closed at the farend, and a mounting structure supporting said are tube within saidjacket comprising a pair of terminals sea-led through the near end ofsaid jacket, a pair of tie rods extending on opposite sides of said aretube substantially its full length and fastened to said terminal-s, apair of end plates supported by said tie rods near opposite ends there-'of, each plate having a central aperture therethrough and the sealbodies of the arc tube being passed through said apertures with the rimof the aperture bearing against the shoulder of the arc tube, one ofsaid end plates being fast to the tie rods, the other of said end platesbeing slidably mounted on said tie rods, and spring means urging theslidably mounted end plate against the arc tube so as to maintain thetie rods in tension and the arc tube in compression in spite ofexpansion of the tie rods from heat during operation of the lamp.

5. A single-ended jacketed arc lamp of great length comprising an innerarc tube having projecting seal bodies at opposite ends, a tubularlight-transmitting jacket surrounding said are tube closed at the farend, and a mounting structure supporting said are tube within saidjacket comprising a closure member at the near end of said jacket havingterminals sealed therethrough, a pair of support rods extending axiallyinwards from said terminals, and a pair of tie rods extending onopposite sides of said are tube substantially its full length, said tierods being fastened to said support rods at ne end, a pair of transverseend plates supported on said tie rods near opposite ends thereof, eachplate having a central aperture therethrough and the seal bodies of thearc tube being passed through said apertures with the rim of theaperture bearing against the shoulder of the arc tube, the near endplate being fast to the tie rods, the far end plate being slidablymounted on said tie rods, coil springs fastened to the tie rods andurging the slidably mounted end plate against the arc tube so as tomaintain the tie rods in tension and the arc tube in compression inspite of expansion of the tie rods from heat during operation of thelamp, and lateral spring blades attached to said end plates and bearingagainst the walls of said jacket to maintain said end plates centeredwithin said jacket.

6. A single-ended jacketed arc lamp of great length comprising anelongated inner arc tube having axially projecting seal bodies atopposite ends with inleads passing there-through, said seal bodiesextending beyond shoulders of the arc tube, a tubular vitreous jacketsurrounding said are tube closed at its far end, and a mountingstructure coaxially supporting said are tube within said jacket, saidmounting structure comprising a vitreous closure of said jacket at thenear end of said lamp, a pair of hollow post terminals sealed into saidclosure member and projecting axially therefrom, support rods fastenedinto said terminals and extending axially inwards therefrom, a pair oftie rods on either side of said are tube extending substantially itsfull length, said tie rods being fastened into said support rods at oneend, a pair of end plates supported by said tie rod-s each having acentral aperture there-through through which the seal body of the arctube extends with the rim of the aperture bearing against the shoulderof the arc tube, the near end plate being fast to the tie rods butinsulated therefrom-the far end plate being slidably mounted on the tierods and likewise insulated therefrom, each tie rod having a coil springcompressed between retaining means therefor on the far end of the tierod and the slidable end plate, said coil springs serving to keep thetie rods under tension and the arc tube compressed between said endplates, spring blades attached to said end plates and bearing againstthe Walls of the jacket to maintain the end plates centered, andalignment rings spaced longitudinally along the tie rods with flexibleblades bearingagainst the inner walls of the jacket to maintain theassembly in alignment.

7. A single-ended jacketed arc lamp of great length comprising anelongated inner arc tube having axially projecting seal bodies atopposite ends with inleads passing therethrough, said seal bodiesextending beyond shoulders of the are tube, a tubular vitreous jacketsurrounding said are tube closed at its far end and a mounting structurecoaxially supporting said are tube within said jacket, said mountingstructure comprising a vitreous closure for said jacket at the near endof said lamp, a pair of hollow post terminals sealed into said closuremember and projecting axially therefrom, support rods fastened into saidterminals and extending axially inwards therefrom, a pair of tie rods oneither side of said are tube extending substantially its full length,said tie rods being fastened into said support rods at one end, a pairof end plates supported by'said tie rods each having a central aperturetherethrough through which the seal body of the arc tube extends withthe rim of the aperture bearing againstthe shoulder of the arc tube, thenear end plate being fast to the tie rods but insulated therefrom, thefar end plate being slidably mounted on the tie rods and likewiseinsulated therefrom, each tie rod having a coil spring compressedbetween retaining means therefor on the far end of the tie rod and theslidable end plate, said coil springs serving to keep the tie rods undertension and the arc tube compressed between said end plates, a flexibleconnector between the far end of one tie rod and the inlead at the farend of the arc tube, the other tie rod being interrupted at a placeclose to said near end plate by an insulator mechanicallyinterconnecting the two parts, a flexible lead inter-connecting the nearpart of said other tie rod and the inlead at the near end of the arctube, spring blades attached to said end plates and bearing against theWalls of the jacket to maintain the end plates centered, and alignmentrings spaced longitudinally along the tie rods with flexible bladesbearing against the inner walls of the jacket to maintain the assemblyin alignment.

References Cited by the Examiner UNITED STATES PATENTS 2,385,435 9/1945Werner et a1. 313278 2,458,218 1/1949 Skehan 313278 X 2,671,183 3/1954St. Louis et al. 313-25 X GEORGE N. WESTBY, Primary Examiner.

ARTHUR GAUSS, Examiner.

C. R. CAMP-BELL, Assistant Examiner.

1. A SINGLE-ENDED JACKETED ARC LAMP OF GREAT LENGTH COMPRISING AN INNERARC TUBE, A TUBULAR LIGHT-TRANSMITTING JACKET SURROUNDING SAID ARC TUBECLOSED AT THE FAR END, AND A MOUNTING STRUCTURE SUPPORTING SAID ARC TUBEWITHIN SAID JACKET COMPRISING TERMINALS SEALED THROUGH THE NEAR END OFSAID ARC TUBE, A PAIR OF TIE RODS EXTENDING ON OPPOSITE SIDES OF SAIDARC TUBE AND FASTENED TO SAID TERMINALS, A PAIR OF TRANSVERSE END PLATESSUPPORTED BY SAID TIE RODS NEAR OPPOSITE ENDS THEREOF, EACH PLATEENGAGING AN END OF THE ARC TUBE, ONE OF SAID END PLATES BEING SLIDABLYMOUNTED ON SAID TIE RODS, AND SPRING MEANS URGING THE SLIDABLY MOUNTEDEND PLATE AGAINST THE ARC TUBE SO AS TO MAINTAIN THE TIE RODS IN TENSIONAND THE ARC TUBE IN COMPRESSION IN SPITE OF EXPANSION OF THE TIE RODSFROM HEAT DURING OPERATION OF THE LAMP.